This invention relates to circuits, for example, a programmable hysteresis comparator circuit.
A typical comparator has first and second inputs for providing an output logic signal. The comparator functions such that if a first signal applied at the first input is greater than a second signal applied at the second input, then the output signal of the comparator is in a first logic state. On the other hand, if the first signal is less than the second signal, then the output signal of the comparator is in a second logic state.
Hystersis is often included in a comparator so as to allow the threshold signal level that determines when the comparator switches from a first logic state to a second logic state to be different the threshold signal level that determines when the comparator switches from a second logic state to a first logic state. As a result, hysteresis typically prevents the output of the comparator from switching logic states for small predetermined perturbations occurring on the first or second signals.
However, most, if not all, comparators do not allow for independent programmability for the high and low hysteresis threshold levels. Further, most, if not all, comparators are not fully differential such that even the hysteresis threshold levels as well as the input and output signals of the comparator are differential.
Hence, there exists a need for a differential comparator having a plurality of programmable hysteresis threshold levels.